Many electric generators such as those commonly utilized in aircraft applications are oil cooled. The oil required for cooling in such generators must be transmitted from a stationary housing to a cylindrical rotor cavity containing the rotating field windings. In addition, a small quantity of oil is needed for cooling a rotating rectifier assembly remote from the rotating field windings and externally of the cylindrical rotor cavity.
To carry the oil for cooling the generator, a number of different arrangements have been proposed. For instance, one arrangement utilized an oil transfer tube that floated, i.e., was not fixed, relative to either the stationary generator housing or the cylindrical rotor cavity, but independent means were required for cooling the rotating rectifier assembly since the oil transfer tube merely served to carry oil from the housing to the cavity containing the field windings. Moreover, due to the floating nature of such oil transfer tubes, they may or may not rotate within the electric generator making them entirely unsuitable for cooling the rotating rectifier assembly.
Among other cooling arrangements in electric generators is that disclosed in Potter U.S. Pat. No. 3,733,503. This cooling arrangement utilizes a rotating rectifier assembly including a plurality of diodes which rotate with a hollow rotor shaft having a small orifice for each diode through which oil carried by the hollow rotor shaft is sprayed on finned surfaces of heat sinks associated with the diodes, and there is no suggestion of the manner of cooling the rotating field windings. Because the hollow rotor shaft rotates with the rotating rectifier assembly, it is necessary to utilize one orifice for each diode and, due to the fact that the oil is sprayed on the finned surfaces of the heat sinks, the cooling is inefficient due to surface thermal boundary effects.
Another cooling arrangement for an electric generator is disclosed in Dafler U.S. Pat. No. 3,629,627. The cooling arrangement of Dafler utilizes a rotating tubular coupling to carry a coolant to a plurality of cooling channels and provides an entirely separate spray nozzle through the stationary housing to direct coolant onto two groups of rectifier devices mounted within and adjacent the housing for rotation relative thereto. As a result, the electric generator is provided with a cooling arrangement which is complex, expensive, and inefficient.
Still another effort to provide a cooling arrangement for an electric generator is that of Jacobson et al U.S. Pat. No. 4,322,030. This cooling arrangement utilizes a stationary cooling feed tube for spraying oil through an orifice to contact the rotating interior surface of an elongated central cavity in an armature shaft. However, the stationary cooling feed tube is utilized solely for this purpose without any suggestion of multiple functions.
While overcoming problems of the type mentioned in connection with the prior art, it is desirable to provide a cooling arrangement for an electric generator utilizing an oil transfer tube fixed relative to a stationary generator housing. It is also desirable to provide such an oil transfer tube adapted to carry oil to a cylindrical rotor cavity for cooling rotating field windings in a large quantity sufficient to fill the rotor cavity while maintaining a predetermined flow rate therethrough. Further, it is desirable to provide a mounting for such an oil transfer tube to prevent rotation at the stationary generator housing end and to accommodate rotation relative to the cylindrical rotor cavity at the opposite end.
Among other desirable features of a cooling arrangement for an electric generator is to combine the cooling components for both the rotating field windings and the rotating rectifier assembly. It is still further desirable to utilize a single orifice for cooling a plurality of rotating diodes where the orifice is stationary and cools the diodes directly rather than through a heat sink in order to avoid surface thermal boundary effects. Additionally, it is desirable to provide an oil transfer tube in a cooling arrangement for an electric generator having two principal functions, i.e., to supply oil to a cylindrical rotor cavity in relatively large quantity and to provide spray oil cooling to a rotating rectifier assembly.
The present invention is directed to overcoming the above stated problems and accomplishing the stated objects.